Vacuum tube for the production of soft x rays



Oct. 2,3, 1928.

I K. W. DAUMANN `VGUUM TUBE FOR THE PRODUCTION 0F SOFT X-RAYS Filed April 15.1926

2 Sheets-Sheet 1 rOcfqz, "1928. 1,888,854

K. W. DAUMANN VACUUM TUBE FOR THE PRODUCTION OF SOFT X-RAYS Filed VApril l5. 1926 2 Sheets-Sheet 2 LMWWS Patented oa. 2 3, 1928.

UNITEDy STATES PATENT OFFICE.

RARI. WILHELMDAUMANN, or HAMBURG, GERMANY, AssIGNoR 'ro c. H. r. MULLER, RONTGHNROHRENFARRIK, or HAMBURG, GERMANY, A CORPORATION vor GER- MANY.`

VACUUM TUBE FOR THE'PRODUCTIONOF SOFT X .RAYS

Application iled April 15, 1926, Serial No. 102,130, and in German-y Apri1 25, 1925.

My present invention relates to X-ray tubes, and particularly to X-ray tubes eniploying incandescent cathodes. The object of my invention is to provide a simple, com- 5 pact and readily cooled vacuum tube of the above indicated class which is adapted for the production of soft- X-rays, Isuch asare used, for instance, for the treatment of skin diseases. An important advantage of the new tube is the fact that it permits to reach a comparatively large field o r area with the X-ray radiation, even when such field or area 1s located close to the lsource from which the X-rays .radiate, or the so-called focal spot.

Satisfactory embodiments of my improved X-ray tube. are illustrated by the accompanying drawings, in which Figs. 1 2 and 3 are longitudinal sections illustratinv vacuum tubes embodyinof'my inventiomPFg.A 3

also indicating suitable electrical circuit arrangements.

In Fig. 1 the anti-cathode body'l-is shownl `as provided with an annular extension 2 the sharp edge portion of'which is connected by fusing with the tubular portion 3 of the vacuum tube. This anti-cathode may be -made of any suitable metal. The inner end of the anti-cathode is provided with a tapering or conical perforation 4, the axis of which is perpendicular to that of the anti-cathode 1. Along a portion of said perforation A4: is located a frusto-conical lining 5, made'of tungsten, tantalum, platinum or other suitable material, and serving for the production of the X-rays. The inner surface of this lining is preferably flush with the adjacent surface of the anti-cathode perforationl.

Located axially within the lining 5yis the in-l 40 Aca'ndescent cathode 6, which may, for instance, bevof the coiled type shown and serves to produce an' vannular focal spot on said lining v5. The free end of the incandescent cathode 6, which is located toward'the wide end of the lining 5, is connected` with a metal diskv 7, the other end of said cathode being secured-'to a tubular metallic carrier 8. This carrier is connected with a glass carrier 9 by fusion and surrounds at a distance 5o a Wire 10, one end of which isfastened to the disk 7 said Wire being arranged axially within the carrier 8, and being preferably separated therefrom by an insulating sleeve 11.

With the glass carrier 9 is connected a glass socket 12, through which eiitend the lead Wires 18, 14, for the supply of the heating the vacuum bulb. At a point in registry with i' the perforation t of the anti-cathode body 1, the vacuum tube is provided with a Window 16, made of glass which has a high degree of permeability to X-rays. For instance, this window may be made of the lithium berate glass known as Lindemann glass. As this window is located in the immediate vicinity of the annular focal spot produced on the lining 5, the exit angle of the bundle of X- rays is relatively large, and the result is that even at a short distance'from said focal spot, a large field or area can be covered by .the X- rays. These rays are of a very soft character, and as their intensity is low, so that they are appreciably absorbed even by the air, it is a materialadvantage to have them spread over a wide field at a very short distance from the vacuumtube. Adjacent to that end of the perforation 4, through which the carrier 8 extends, the latter is provided with a disk 17, serving as a screen to prevent the escape of X-rays in that direction, that is, towards the tubular portion 15. In order to keep the anti-cathode bod 1 cool, itis made or connected with a coo ing rod 18, the outer end of which projects beyond the tube 3 and is preferably provided at its exposed portion with heat radiating disks or fins 19. j

In operating the tube described above, I connect the anticathode/.with the positive pole of a source of high potential current, for. instance, from 20,000 to 25,000 volts, while the cathode 6 is connected with the negative pole of said source. The heating current is supplied in the well known/ manner to the cathode 6, through thev wires 13, 14, so that I scribed, these X-rays can escape from the 'vacuum tube,"onl'y through the window 1.6, the' escape of the X-rays in the o posite `direction being prevented by the di or screen 17 radiating appliance 19, so that they heat isy The heat produced at the lining finds a short way to the outside through the cooling rod 18, provided V with the fins or other h'eat quickly dissipated, and premature destruction of the anti-cathode, and particularly of its lining 5, is prevented.

The X-ray tube shown in Fig. 2 is of the same general character as the one shown in Fig. 1. The .perforation 4, however, is'not arranged at right angles to the axis of the anti-cathode 21, but colaxially` therewith. This anti-cathode, which is ,of tubular character, practically forms a portion of the outer wall of the tube. The metallic carrier 8 of .the incandescent cathode 6 is, in this form of the invention, located within the anti-cathode and extends lengthwise thereof. A cooling sleeve 18,.made of metal and provided with heat radiating disks'or fins 19, is slipped directly on the outer surface of the anti-cathode 21. The window 16 through which the soft X-rays leave the X-ray tube is, in this form of my invention also, located inthe longitudinal axis of the anti-cathode body 1, and in axial alignment with the frusto-conlcal sleeve or lining 5. The construction shown in Fig. 2

-. Fig. 1. Therefore,

affords even a better dissipation of the heat from the X-raytube, according to Fig.,1, for the reason that the distance from the lining 5 to thecooling body 1,8, is shorter than the distance from the lining 5 to the cooler 18, 19, and furthermore,thecross section of the bodies which are employed to car lthe heat away from the lining 5, is greater 1n Fig. 2 than in Fig. 2 will be ableto stand a higher load than the one according to Fig. 1. Furthermore, the glass portions of the tube shown in Fig.

2 can be protected readily by surroundingl jackets made of suitable materi'al for instance, the one known under the trade name of Pertinax.

The exhaustiori of` a tube constructed according to Fig. 2 isF preferably conducted by first heating'the "ent-1re vacuum. tube in a Ipump box to a temperature of from 400 to 450l centigrade, according. to the temperature which the 'glass employed can withstand, and at the same time the Lindemann window which at such tem erature would become soft, is cooled by lowing cold air against it.- Atthe same time the vcathode is brought to incandescence by-'passing a current through it. ...After this -operation"has been lcontinued for a su-icie'nt'f-flength 'of time,

the aliode or anti-cathodeV of' the tube is heated to red heat by an external source of heat, for instance, b'y means of an annular I. gs burner or'an electric heating body of corpondingshape, and the vacuum pum is o rated to remove air from the tube. A ter h t e removal of air has beencontinued to the --proper point,`the vacuum tube is filled with a '.-purel rare gils, for instance, helium or neon,

the tube according to` until the function of the tube remains uniform or constant at a pressure of about 10-2 millimeters of mercury. When this condition has been attained the vacuum tube is sealed off from the pump by fusion, in the well known manner. y

With a tube constructed according to Fig. 2, the anti-cathode can be readily grounded in such la manner that the attendant can not` touch any part carrying high voltage current, and therefore the attendant will not be4 exposed to any danger of shocks. p For this purpose, as shown in Fig. 3, the tubular anti- `.cathode 21 of the vacuum tube 2O is connected with a metal hose 28, by a metal sleeve 29. -This metal hose 28 is grounded by being connected with one terminal 26 of the high tension transformer 27, which terminal is grounded at 31. The other terminal 26l of the secondary ofsaid transformer 27 is connected with the terminal' 24 of the auxiliary transformer 25,l which is employed to supply the heating current to the mcandescent cathode 22, by means of wires 23, which may be conducted through a tube 32 made of vrubber or other insulating material. The glass wall of the vacuum tube 20 may be insulated fromthe metal .sleeve 29, by means lof a sleeve 30 made of rubber or other in- `sulating material. It'will be noted that the anti-cathode 1, 2 (Fig. 1) or 21 (Figs. 2 and 3) virtually forms a portion ofthe wall of the X-ray tube' andis therefore very firmly supported and not liable to be thrown out of its properposition by jars or otherinuences.

Various modifications may be made without departing from the nature of my invention as defined in the appended claims.

I claim as my invention:

1. A vacuum tube for the. production of lun soft X-rays, comprising an incandescent cathode, a flarlng anti-cathode surrounding said cathode at a distance, a window of a lmaterial of high permeability7 to X-rays, 1o-

cated in line with the longitudinal axis of the cathode at -that toward which sa1d anti-cathode flares, and `a disk or screen likewise located in line with the longitudinal axisof the cathode, but at the opposite side. of the X-ray producing antiportion of the lvacuum tube llc) cathode, to prevent the X-rays from lssuing anti-cathode, grenades. l

tube-.for the production of said vmetal-hose being 0 l ametal oeesurroundlngsaid wires and connected soft X-rays, comprising an evacuated bulb ing Within said chamber and adptedto prolprovided with a Window of higher permeduce an annular focal zone upon the inner ability to X-rays than the other portions of surface of the anti-cathode. 10 the bulb, an anticuthode constituting vir- In testimony whereof I have hereunto set 5 tually a'portion of the Wall of said bulb and my hand.

forming al chamber which flares toward Said window, and 8,11 incandescent cathode extendl KARL WILHELM DAUMANN. 

